Dual layer electrophotographic photoreceptor comprises titanium phthalocyanine charge generator and hydrazone charge transport materials

ABSTRACT

A dual layer photoreceptor for use in electrophotography, wherein a charge transport layer containing a hydrazone compound and a binder polymer is laminated on a charge generation layer containing a titanium phthalocyanine compound of the formula: ##STR1## wherein X represents hydrogen atom, lower alkyl group, lower alkoxy group, allyloxy group, nitro group, cyano group, hydroxy group, benzyloxy group or halogen atom, Y represents halogen atom, alkoxy group or oxygen atom, n represents an integer of 1 or 2 and m represents an integer of 0 to 4, and a binder polymer, formed on an electroconductive substrate.

BACKGROUND OF THE INVENTION

This invention relates to a dual layer photoreceptor for use inelectrophotography having a high sensitivity upto the near infraredwavelength region.

Heretofore, inorganic photoconductive materials such as selenium,cadmium sulfide and zinc oxide have widely been used for photoreceptorsfor electrophotography.

Moreover, organic photoconductive materials represented bypolyvinylcarbazole have been investigated as well to be applied to thephotoreceptors for electrophotography, and several of them have alreadybeen put into practical use.

The organic photoconductive materials have various merits, for example,in that they are reduced in weight, can be formed into films withoutdifficulty and facilitate the production of the photoreceptor ascompared with the inorganic materials.

Along with the recent prevalency of laser beam printer or the like thatuses a laser beam as light source instead of conventional incandescentlight and has advantages in higher printing speed, higher picturequality and non-impact printing, development for photosensitivematerials capable of satisfying the requirements therefor has beendemanded.

A semiconductor laser has been remarkably developed in recent yearsamong the laser beams. In this case, since the wavelength of thesemiconductor laser is around 800 nm, a photoconductive material of aproperty highly sensitive to the long wavelength ray around 800 nm hasstrongly been desired.

As the organic substance capable of satisfying the above-mentionedrequirement, there have been known squaric acid methine dye, indolinedye, cyanine dye, pyrylium dye, polyazo dye, phthalocyanine dye,naphthoquinone dye and the like. However, at the present stage, thesquaric acid methine dye, indoline dye, cyanine dye and pyrylium dye areinsufficient in the practical stability, i.e., cyclic characteristicsalthough they are adaptable to the longer wavelength, the polyazo dye isless adaptable to the longer wavelength and disadvantageous in view ofthe production thereof and the naphthoquinone dye is disadvantageous inview of the sensitivity.

The photoreceptor composed of a metal phthalocyanine compound among thephthalocyanine dyes, has a sensitivity peak at a relatively longerwavelength region of from 700 to 750 nm, while it somewhat variesdepending on the central metal, as described in U.S. Pat. No. 3,357,989,Japanese Patent Application Laid-Open No. 11136/1974, U.S. Pat. No.4,214,907 and British Patent No. 1268422, etc. However, the sensitivityis gradually reduced in excess of 750 nm, and turned into no morepractically effective level.

Japanese Patent Application Laid-Open No. 49544/1984 describes anelectrophotographic photoreceptor in which titanium phthalocyanine isvapor-deposited on a substrate to prepare a charge generation layer, anda charge transport layer mainly composed of2,6-dimethoxy-9,10-dihydroxyanthracene is prepared by coating. However,this photoreceptor material has a high residual potential to suffer froman unfavorable restriction to some extent in the practical use, and isless advantageous in view of the reproducibility of various electricproperties due to the unevenness in the film thickness formed by thevapor-deposition. Furthermore, it bears some inevitable restrictions inthe mass production of the photoreceptor in industrial scale. On theother hand, problems are resulted to the photoreceptor itself such asoccurrence of interference fringe mainly attributable to the reflectionof the laser beam on the substrate at the time of the exposure, whileseveral technics have been known as the countermeasures therefor.

As one of such measures, there has been known a method of increasing thethickness of the charge generation layer to absorb the exposing laserbeam, thereby eliminating the reflection from the substrate. But thereis a limit to the thickness of the film that can be formed by theconventional vapor-deposition process and the thickness control is alsodifficult.

On the contrary, a method of preparing the charge generation layer bycoating pigment dispersed binder solution is advantageous since thismethod can prepare the layer with an optional thickness at goodreproducibility under easy control, requires no high vacuum system forthe vapor-deposition, can avoid heat decomposition or degradation whileheating, and additionally it is free from cumbersome procedures in theindustrial production such as crystallization of vapor-depositedproducts in various ways after vapor-deposition as in the vapordeposition process.

The object of the present invention is to provide an organicphotoconductive material capable of producing the photoreceptor having ahigh sensitivity at around 800 nm, while having a desired chargingproperty, extremely low residual potential and satisfactory durability.

SUMMARY OF THE INVENTION

The aimed object of this invention can be attained by coating a bindersolution containing titanium phthalocyanine as the charge generationmaterial to form the charge generation layer and, further, byincorporating a hydrazone compound among various known materials as thecharge transport material of the charge transport layer formed on thecharge generation layer.

Specifically, the feature of this invention lies in a dual layerphotoreceptor for use in electrophotography, wherein a charge transportlayer is formed on a charge generation layer overlaid on anelectroconductive support, characterized in that the charge generationlayer contains a titanium phthalocyanine compound represented by thefollowing general formula I: ##STR2## wherein X represents a hydrogenatom, a lower alkyl group, a lower alkoxy group, an allyloxy group, anitro group, a cyano group, a hydroxy group, a benzyloxy group or ahalogen atom, Y represents a halogen atom, an alkoxy group or an oxygenatom, n represents an integer of 1 or 2 and m represents an integer from0 to 4, and a binder polymer, and that the charge transport layercontains a hydrazone compound and a binder polymer.

DETAILED DESCRIPTION OF THE INVENTION

Referring now more specifically to this invention, the titaniumphthalocyanine contained in the photoconductor layer of theelectrophotographic photoreceptor according to this invention isrepresented by the above-mentioned general formula I.

In the general formula I, X represents a hydrogen atom; a lower alkylgroup such as methyl group and ethyl group; a lower alkoxy group such asmethoxy group and ethoxy group; an allyloxy group; a nitro group; acyano group; a hydroxy group; a benzyloxy group; or a halogen atom suchas bromine atom or chlorine atom. Y represents a halogen atom such aschlorine atom and bromine atom; an alkoxy group such as methoxy groupand ethoxy group; or an oxygen atom.

Those in which X represents hydrogen atom or methyl group and Yrepresents an oxygen atom are particularly preferred.

The titanium phthalocyanine may be synthesized in accordance with theknown reaction scheme as described below. ##STR3##

Preferred organic solvents have high boiling points and are inert to thereaction, such as quinoline, α-chloronaphthalene, β-chloronaphthalene,α-methylnaphthalene, methoxynaphthalene, diphenyl ether, diphenylmethane, diphenyl ethane, ethylene glycol, dialkyl ether and higheraliphatic amines. A desired reaction temperature is usually from 200° C.to 300° C. As the case may be, the reaction may be proceeded by heatingto a temperature higher than 160° C. without the solvent.

In accordance with the above-mentioned reaction scheme, the resultedtitanium phthalocyanine compound is in the form of PcTiCl₂ wherein Pcrepresents the phthalocyanine residue, but PcTiO is also formedpartially through the hydrolysis and the product is usually obtained asthe mixture thereof. Complete hydrolysis may also be attained by aqueousammonia treatment (at 100° C.) or the like (refer to Japanese PatentApplication Laid-Open No. 166959/1984).

As the starting phthalonitrile, known o-dicarboxylic acids, phthalicacid anhydrides, phthalimides and phthalic diamides may also be used.

The titanium phthalocyanine compound obtained as described above can bepurified in the same manner as in general organic dyes through knownmethods such as sublimation, recrystallization, treatment with organicsolvent, heat suspending purification with high boiling organic solvent,re-precipitation after dissolution with sulfuric acid, alkali washing,etc. The purification is applied not only for the removal of impuritiesbut also for the hydrolysis of PcTiCl₂ Since electrical properties ofthe phthalocyanine compound obtained in accordance with the foregoingreaction scheme are significantly varied, it is preferred to use suchpurified phthalocyanine.

The organic solvent usable for the organic solvent treatment and heatsuspending purification may include xylene, naphthalene, toluene,monochlorobenzene, trichlorobenzene, o-dichlorobenzene, chloroform,tetrachloroethane, acetoamide, N,N-dimethylformamide,N,N-dimethylacetoamide, N-methylpyrrolidone, etc., as well as thoseorganic solvents used in the aforementioned reaction, water, and otherorganic solvents such as methanol, ethanol, propanol, butanol, pyridine,acetone, methyl ethyl ketone and tetrahydrofuran. High boiling organicsolvent such as N-methylpyrrolidone is particularly preferred for theheat suspending purification.

The binder polymer may include polymer or copolymer of vinyl compoundsuch as styrene, vinyl acetate, methyl acrylate, ethyl acrylate, benzylacrylate and methacrylate; polyester; polycarbonate; polysulfone;polyvinyl butyral; phenoxy resin; cellulose resins such as celluloseester and cellulose ether; urethane resin and epoxy resin. The amount ofthe binder polymer to be incorporated usually ranges from 0.1 to 5 timesby weight of the titanium phthalocyanine compound.

It is desired that the phthalocyanine compound is present in the form ofminute particles of less than 1 μm in the binder.

The hydrazone compound as the main ingredient in the charge transportlayer is represented by the following general formula IIA or IIB:##STR4## wherein R¹ represents an alkyl group such as methyl group,ethyl group and butyl group, a substituted alkyl group, an aralkyl groupsuch as benzyl group, an allyl group or an alkoxycarbonyl ethyl groupsuch as methoxycarbonyl ethyl group, ethoxycarbonyl ethyl group andbutoxycarbonyl ethyl group, R² represents an alkyl group such as methylgroup, ethyl group, propyl group and butyl group, an allyl group, asubstituted alkyl group, a phenyl group, a naphthyl group or an aralkylgroup such as benzyl group, R³ represents a hydrogen atom, an alkylgroup such as methyl group and ethyl group, an alkoxy group such asmethoxy group and ethoxy group, or a halogen atom such as chlorine atomand bromine atom; and ##STR5## wherein X¹, Y¹ and R⁵ each represents ahydrogen atom, a lower alkyl group such as methyl group, ethyl group,propyl group, butyl group and hexyl group, a dialkyl amino group such asdimehylamino group and diethylamino group, a lower alkoxy group such asmethoxy group, ethoxy group, propoxy group and butoxy group, or an arylalkoxy group such as phenoxy group, benzyloxy group and phenethyloxygroup, R⁴ represents a hydrogen atom, a lower alkyl group such as methylgroup, ethyl group, propyl group, butyl group and hexyl group, an allylgroup, a phenyl group, or an aralkyl group such as benzyl group andphenethyl group, m¹ and l each represents an integer of 1 or 2 and prepresents an integer of 0 or 1.

Particularly preferred are those represented by the general formula IIAin which R¹ represents methyl group or ethyl group, R² represents methylgroup or phenyl group and R³ represents hydrogen atom, or thoserepresented by the general formula IIB in which X¹ and Y¹ eachrepresents methoxy group, R⁴ represents methyl group or phenyl group, R⁵represents hydrogen atom, m¹ and l each represents 1 and p represents 0.

Examples of the hydrazone compound indicatively shown in Tables 1 and 2below.

                  TABLE 1                                                         ______________________________________                                        Compound                                                                      No.         R.sup.1   R.sup.2      R.sup.3                                    ______________________________________                                        13          CH.sub.3                                                                                 ##STR6##    H                                          14          C.sub.2 H.sub.5                                                                          ##STR7##    H                                          15          C.sub.3 H.sub.7.sup.(n)                                                                 CH.sub.3     H                                          16          C.sub.2 H.sub.5                                                                         CH.sub.3     H                                          17          C.sub.2 H.sub.5                                                                          ##STR8##    CH.sub.3                                   18          C.sub.2 H.sub.5                                                                          ##STR9##    H                                          ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Compound                                                                      No.     X.sup.1  m.sup.1                                                                              Y.sup.1                                                                              l   p   R.sup.4                                                                              R.sup.5                         ______________________________________                                        19      OCH.sub.3                                                                              1      OCH.sub.3                                                                            1   0                                                                                  ##STR10##                                                                           H                               20      CH.sub.3 1      CH.sub.3                                                                             1   0   CH.sub.3                                                                             H                               21      OCH.sub.3                                                                              1      OCH.sub.3                                                                            1   1                                                                                  ##STR11##                                                                           H                               ______________________________________                                    

The charge generation layer may be obtained, for instance, by preparinga coating solution by dissolving or dispersing the titaniumphthalocyanine compound of the general formula I singly or together withthe binder polymer in an appropriate solvent and then coating it to dryon an electroconductive support.

The charge generation layer is usually coated in a thickness in the 0.1to 1 μm range.

The solvent for preparing the coating solution may include a basicsolvent such as butyl amine and ethylene diamine, ethers such astetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane and diethyleneglycol dimethyl ether; ketones such as methyl ethyl ketone andcyclohexanone; aromatic hydrocarbons such as toluene and xylene;non-protonic polar solvents such as N,N-dimethylformamide, acetonitrile,N-methylpyrrolidone and dimethyl sulfoxide; alcohols such as methanol,ethanol and isopropanol; esters such as ethyl acetate, methyl formateand methyl cellosolve acetate; and chlorinated hydrocarbons such asdichloroethane and chloroform. These solvents may be used singly or as amixture of two or more of them. If the binder polymer is used, thesolvents are desired to be able to dissolve the polymer.

As the electroconductive support on which the charge generation layer iscoated, any of well-known electroconductive supports employed in theelectrophotographic photoreceptor can be used. Specific examples mayinclude, for example, drums or sheets of metals such as aluminum andcopper, or laminates of foils and vapor-deposition products of thesemetals. Furthermore, plastic films, plastic drums, paper or paper tubeswhich are conductive by coating electroconductive substances such asmetal powder, carbon black, copper iodide and polymeric electrolytestogether with an appropriate binder can also be mentioned. Furthermore,there can also be mentioned those plastic sheets or drums which becomeconductive by the incorporation of electroconductive materials such asmetal powder, carbon black and carbon fibers.

The charge transport layer is formed by coating on the charge generationlayer as described above. On the contrary, the charge transport layermay be formed on the electroconductive substrate and the chargegeneration layer may be coated thereover. However, since the thicknessof the charge generation layer is thin, the former type is usuallyemployed for protecting the charge generation layer from abrasion orcontamination.

The charge transport layer serves to transport charge carrier generatedin the charge generation layer and contains a charge carriertransporting medium which is the hydrazone compound as described above.The charge carrier transporting medium is usually incorporated in anamount of from 0.2 to 1.5 times by weight and, preferably, from 0.3 to1.2 times by weight of the binder polymer.

The same polymer as incorporated into the charge generation layer may beused as the binder polymer of the charge transport layer, and it isdissolved together with the charge carrier transporting medium into asolvent to prepare a coating solution, which is then coated and dried toform the charge transport layer. The thickness of the charge transportlayer is from 5 to 50 μm and, preferably, from 10 to 30 μm.

The photosensitive layer of the electrophotographic photoreceptoraccording to this invention may, of course, additionally contain awell-known sensitizer. A preferred sensitizer may include Lewis acidsand dye pigments forming a charge transfer complex with the organicphotoconductive substance. The Lewis acid may include electron acceptingcompounds, for example, quinones such as chloranil,2,3-dichloro-1,4-naphthoquinone, 2-methylanthraquinone,1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone,2-chloroanthraquinone and phenanthrenequinone; aldehydes such as4-nitrobenzaldehyde; ketones such as 9-benzoylanthracene, indandione,3,5-dinitrobenzophenone and 3,3',5,5'-tetranitrobenzophenone; acidanhydrides such as phthalic anhydride and 4-chloronaphthalic acidanhydride; cyano compounds such as tetracyanoethylene, terephthalalmalononitrile, 4-nitrobenzal malononitrile and4-(p-nitrobenzoyloxy)benzal malononitrile; and phthalides such as3-benzal phthalide, 3-(α-cyano-p-nitrobenzal)phthalide and3-(α-cyano-p-nitrobenzal)-4,5,6,7-tetrachloro phthalide. The dyes mayinclude, for example, triphenyl methane dyes such as methyl violet,brilliant green and crystal violet, thiazine dye such as methylene blue,quinone dyes such as quinizarin, cyanine dyes and pyrylium salt,thiapyrylium salt and benzopyrylium salt and others.

Further, the photosensitive layer of the electrophotographicphotoreceptor according to this invention may also be incorporated witha well-known plasticizer for improving the film-forming property,flexibility and mechanical strength. The plasticizer may include, forexample, phthalic acid ester, phospholic acid ester, epoxy compound,chlorinated paraffin, chlorinated aliphatic acid ester and aromaticcompound such as methyl naphthalene. The photoreceptor may also have, asrequired, an adhesive layer, an intermediate layer or a transparentinsulation layer.

The photoreceptor produced from the phthalocyanine compound according tothis invention has an extremely high sensitivity to the incandescentlight as well, shows less potential variation after repeating use andhas an extremely high spectral sensitivity within a range from 750 to900 nm.

Accordingly, the photoreceptor is suitable for the laser printer usingsemiconductor laser beam as the optical source which have been greatlydeveloped recently.

This invention will be explained more specifically on the method ofpreparing the photoreceptor from the materials as described above and onthe electrical properties thereof, while referring to examples. Itshould, however, be noted that this invention is no way limited to thefollowing examples so long as it is within the scope of the invention.

In Examples, "parts" means "parts by weight".

Preparation Example 1

Phthalodinitrile (4.6 parts) was added into 25 parts ofα-chloronaphthalene and dissolved at 120° C. Then, 1.7 g of TiCl₄ wasdropped and continuously stirred at 150° C. for 30 minutes. Then, thereaction temperature was gradually increased and the stirring wascontinued at 220° C. for two hours.

After the reaction was over, the reaction solution was left to cool andfiltered while hot when the temperature of the reaction system waslowered to 100° C. Then the filtrate was subjected to methanol heatsuspension, boiling water suspension and heat suspension withN-methylpyrrolidone at 120° C. for one hour, which was then filteredwhile hot, subjected to methanol heat suspension again and filtered andthen dried at a reduced pressure to obtain 2 parts of blue powder(Compound No. 1).

Elemental analytical values for Compound No. 1 are as described below.

    ______________________________________                                                      C %  H %      N %    Cl %                                       ______________________________________                                        Calculated                                                                              PcTiCl.sub.2                                                                            60.87  2.56   17.75                                                                              11.23                                  value     PcTiO     66.68  2.78   19.45                                                                              --                                     Measured value  66.85  3.01     19.53                                                                               0.49                                    ______________________________________                                    

As the result of the elemental analysis shown above, it can be seen thatthe titanium phthalocyanine compound obtained in Preparation Example 1is a mixture of PcTiCl₂ and PcTiO, almost of which being PcTiO.

Titanium phthalocyanine of Compounds No. 2-No. 12 shown in Table 3 weresynthesized according to the same procedures as in Preparation Example1.

                  TABLE 3                                                         ______________________________________                                         ##STR12##                     I                                              Compound                                                                      No.     X           m     Y     n   Remarks                                   ______________________________________                                        2       H           0     O     1   elemental ana-                                                                lytical value:                                                                Cl content 0.5%                           3        H          0     O     1   elemental ana-                                                                lytical value:                                                                Cl content 5%                             4       H           0     OC.sub.4 H.sub.9                                                                    2                                             5       CH.sub.3    1     O     1                                             6       OH          1     O     1                                             7       3-NO.sub.2  1     O     1                                             8       4-NO.sub.2  1     O     1                                             9       OCH.sub.3   4     Cl    2                                             10      Cl          4     O     1                                             11                                                                                     ##STR13##  4     O     1                                             12      CN          1     O     1   elemental ana-                                                                lytical value:                                                                Br content 0.3%                           ______________________________________                                    

EXAMPLE 1

0.4 parts of the titanium phthalocyanine compound of Compound No. 1 wasdispersed by a sand grinder with 30 parts of4-methoxy-4-methylpentanone-2, to which was added 0.2 parts of polyvinylbutyral. The thus obtained dispersed mixture of the titaniumphthalocyanine compound was coated with a film applicator and then driedto a dry film thickness of 0.3 g/m² on an aluminum layer which had beenvapor-deposited on a polyester film of 100 μm thickness. Onto the thusobtained charge generation layer, a solution prepared by dissolving 90parts of the hydrazone compound of Compound No. 19 shown in Table 2 and100 parts of a methacrylic resin (DIANAL BR-85, trademark of the productmanufactured by Mitsubishi Rayon K.K.) into 550 parts of toluene wascoated so that the film dry thickness of 13 μm was attained to form acharge transport layer. In this way, an electrophotographicphotoreceptor having a photosensitive layer composed of two layers wasobtained.

The value of half-decay exposure intensity (E_(1/2)) of thephotosensitive material was measured as the sensitivity thereof andshown in Table 1.

The half-decay exposure intensity of the photoreceptor was determinedusing an electrostatic paper analyzer (Model SP-428, manufactured byKawaguchi Denki Seisakusho). The photoreceptor was at first charged withcorona discharge at -5.5 KV in the dark and then exposed to incandescentlight at a illumination of 5 lux and measured the exposure intensityE_(1/2) (lux.sec) required till the surface potential decayed toone-half of the initial surface potential.

The spectral sensitivity was determined as the half-decay exposureenergy sensitivity (μJ/cm²) by irradiating a light at 0.4 μW/cm²separated through a spectrofilter.

For estimating the cyclic characteristics, the photoreceptor is chargedat -5.5 KV and irradiated with a light of 200 lux for 2 sec. Afterrepeating the procedure at 2.4 sec/cycle, the charged potential, theresidual potential and the degradation in the sensitivity were measured.The results are shown in the following tables.

    ______________________________________                                        Initial                                                                              Incandescent        Wavelength at                                      charged                                                                              light sensitiv-                                                                          Residual the maximum                                                                             Maximum                                  voltage                                                                              ity        potential                                                                              spectrum sen-                                                                           sensitivity                              V      E.sub.1/2  (lux · sec)                                                          V        sitivity nm                                                                             μJ/cm.sup.2                           ______________________________________                                        -535   0.97       -15      800       0.4                                      ______________________________________                                        Repeating Characteristics                                                               Charged      Residual   Sensitivity                                           potential (V)                                                                              potential (V)                                                                            (lux · sec)                        ______________________________________                                        Initial   -520         -17        1.0                                         After     -510         -20        1.05                                        2,000 cycles                                                                  ______________________________________                                    

Since electrical characteristics are preferred and, among all, theresidual potential value is low, the photoreceptor is found to besatisfactory.

EXAMPLE 2

A charge generation layer was prepared quite in the same procedures asin Example 1 from the titanium phthalocyanine compound of CompoundNo. 1. Onto the thus obtained charge generation layer, a solutionprepared by dissolving 90 parts of the hydrazone compound of CompoundNo. 16 shown in Table 1 and 100 parts of polycarbonate (NOVAREX 7030A,trade name of the product manufactured by Mitsubishi Chemical IndustriesLtd.) into 600 parts of tetrahydrofuran was coated so as to obtain 13 μmof dry film thickness to prepare a charge transport layer.

The initial property and the repeating property of the thus obtainedelectrophotographic photoreceptor were determined in the same proceduresas in Example 1. The results are shown in the following tables.

    ______________________________________                                        Initial                                                                              Incandescent        Wavelength at                                      charged                                                                              light sensi-                                                                             Residual the maximum                                                                             Maximum                                  potential                                                                            tivity     potential                                                                              spectrum sen-                                                                           sensitivity                              V      E.sub.1/2  (lux · sec)                                                          V        sitivity nm                                                                             μJ/cm.sup.2                           ______________________________________                                        -550   0.8        -10      800       0.35                                     ______________________________________                                        Repeating Characteristics                                                               Charged     Residual    Sensitivity                                           potential (V)                                                                             potential (V)                                                                             (lux · sec)                        ______________________________________                                        Inital    -550        -15         0.8                                         After     -560        -22         0.95                                        10,000 cycles                                                                 ______________________________________                                    

The electrical properties above are excellent and, among all, theresidual potential value is extremely low, and moreover, the stabilityunder the repeating use is found to be satisfactory.

EXAMPLES 3-13

Photoreceptors comprising the substances shown in the following Table 4were produced in accordancde with the procedures in Examples 1 and 2 andelectrical properties were measured in the same manner as in Example 1.

                  TABLE 4                                                         ______________________________________                                               Titanium               Charged                                         Example                                                                              phthalocyanine                                                                            Hydrazone  potential                                                                            Sensitivity                              No.    compound    compound   (V)    (lux · sec)                     ______________________________________                                        3      Compound    Compound   -523   1.2                                             No. 2       No. 13                                                     4      Compound    Compound   -498   1.8                                             No. 3       No. 16                                                     5      Compound    Compound   -513   0.8                                             No. 5       No. 18                                                     6      Compound    Compound   -506   0.9                                             No. 9       No. 15                                                     7      Compound    Compound   -479   0.8                                             No. 4       No. 16                                                     8      Compound    Compound   -556   0.9                                             No. 7       No. 14                                                     9      Compound    Compound   -581   0.8                                             No. 9       No. 21                                                     10     Compound    Compound   -525   0.9                                              No. 10     No. 20                                                     11     Compound    Compound   -563   0.8                                             No. 1       No. 17                                                     12     Compound    Compound   -498   0.9                                              No. 12     No. 19                                                     13     Compound    Compound   -486   1.0                                             No. 6       No. 13                                                     ______________________________________                                    

What is claimed is:
 1. A dual layer photoreceptor for use inelectrophotography, wherein a charge transport layer is laminated on acharge generation layer overlaid on an electroconductive substrate,characterized in that the charge generation layer contains a titaniumphthalocyanine compound represented by the following general formula I:##STR14## wherein X represents a hydrogen atom, a lower alkyl group, alower alkoxy group, an allyloxy group, a nitro group, a cyano group, ahydroxy group, a benzyloxy group or a halogen atom, Y represents ahalogen atom, an alkoxy group or an oxygen atom, n represents an integerof 1 or 2 and m represents an integer of 0 to 4, and a binder polymer,and that the charge transport layer contains a hydrazone compound and abinder polymer.
 2. The dual layer photoreceptor for use inelectrophotography as claimed in claim 1, wherein the binder polymerincorporated into the charge generation layer and the charge transportlayer is a polymer or copolymer of vinyl compound, polyester,polycarbonate, polysulfone, polyvinyl butyral, phenoxy resin, celluloseresin, urethane resin or epoxy resin.
 3. The dual layer photoreceptorfor use in electrophotography as claimed in claim 1 or 2, wherein thehydrazone compound is represented by the following general formula IIAor IIB: ##STR15## wherein R¹ represents an alkyl group, a substitutedalkyl group, an aralkyl group, an allyl group or an alkoxy carbonylethyl group, R² represents an alkyl group, an allyl group, a substitutedalkyl group, a phenyl group, a naphthyl group or an aralkyl group, andR³ represents a hydrogen atom, an alkyl group, an alkoxy group or ahalogen atom; and ##STR16## wherein X¹, Y¹ and R⁵ represent a hydrogenatom, a lower alkyl group, a dialkyl amino group, a lower alkoxy group,a phenoxy group or an allyl alkoxy group, respectively, R⁴ represents ahydrogen atom, a lower alkyl group, an allyl group, a phenyl group or anaralkyl group, m¹ and l represent an integer of 1 or 2, respectively,and p represents an integer of 0 or 1.